1. Field of the Invention
The present invention relates to a brushless direct current motor, and has as an object to reduce vibrations and noise to a greater degree than can be achieved in related art.
2. Description of the Related Art
Brushless direct current motors are widely used in various fields. In connection with driving of motors used to drive fans, among such motors, WO 2007/040180 and WO 2009/110219 disclose a feature of calculating air volume on the basis of the rotation speed and electric drive current of a motor to control driving of the motor, thereby reducing a change in a flow (the air volume) caused by a change in a load. Meanwhile, Japanese Patent No. 3653670 and so on disclose a feature of controlling a motor with so-called vector control. In addition, in recent years, in driving of a motor of this type, a method of driving, with sinusoidal signals, driving elements which output drive voltages for phases of the motor to reduce vibrations and noise of the motor has often been adopted.
It is generally desirable that vibrations and noise of a motor be reduced to a greater degree.
The present invention has been made in view of the above circumstances, and has as an object to reduce vibrations and noise of a motor to a greater degree than can be achieved in related art.
The present inventors have conceived the idea of causing the amplitude of a drive voltage for driving a driving element to vary in a complementary manner in relation to a voltage fluctuation so as to cancel a fluctuation in an electric drive current caused by a fluctuation in power for driving, and completed the present invention.